The biological effects of oxidizing pollutants such as ozone and high-energy ionizing radiation, are thought to be mediated by the superoxide radical O2-, though its basic chemistry is not yet well known. The finding of high concentrations of superoxide dismutase (the enzyme which destroys O2-) in lung tissue suggests a possible first defense line against such pollutants. The oxidative attack of such agents upon living cells leads to structural damage of biological membranes. Many of the currently proposed mechanisms on the interaction of superoxide radicals with biological systems are in conflict on whether the immediate reactive species is actually the O2-, or its suggested disproportionation product 1O2 (singlet molecular oxygen), or its reaction product with hydrogen peroxide, the hydroxyl radical (Haber-Weiss reaction). We have studied some reactions of O2- by the accurate and convenient techniques of pulse radiolysis and continuous-flow and stopped-flow radiolysis. We propose to combine the techniques of radiation chemistry and biochemistry to carry out the following reaction-kinetic studies. (a) The reactions of O2- with compounds of biological interest, e.g. metal-chelates, substrates, coenzymes and enzyme systems. (b) A thorough study of the uncatalyzed and catalyzed reaction of O2- with hydrogen peroxide at neutral pH. (c) The reactions of singlet molecular oxygen with those selected compounds in (a) which are not reactive toward O2-. (d) Biological membranes; various oxygen species and derivatives from above will be tested on membranes to determine their role in lipid peroxidation and their deleterious effect on membranes enzymes. All reactions will be investigated on a quantitative basis with complete product analysis, essential for mechanism studies.